An assessment of mast-cell deficient mice (W/Wv) as a model system to study the role of histamine in implantation and deciduoma formation.

The ovaries from mast cell-normal (+/+) and mast cell-deficient (W/Wv) mice were examined with light and electron microscopy. In addition the effect of ovariectomy and subsequent steroid treatment on total uterine histamine content, total mast cell numbers and surface and glandular epithelial cell heights was measured. The ovaries of +/+ mice were normal, displaying various stages of follicular growth and atresia and numerous corpora lutea; the ovaries of W/Wv mice lacked follicles and corpora lutea but contained numerous hyperplastic interstitial cells which contained numerous lipid droplets, vesiculated mitochondria and abundant endoplasmic reticulum suggestive of steroid synthesis. Steroid treatment of ovariectomized +/+ and W/Wv mice caused a significant increase in uterine wet weight and endometrial surface and glandular epithelial cell heights. In +/+ mice, steroid treatment caused a concomitant increase in total mast cells per uterine horn while mast cells were totally absent in W/Wv mice. The increase in uterine histamine in +/+ mice is consistent with the increase in mast cell numbers. Measurable amounts of uterine histamine, which increases slightly after steroid treatment, were demonstrated in W/Wv mice. Since the uteri of +/+ and W/Wv mice respond to steroids in a similar manner with the sole exception being histamine content and mast cell numbers, our results demonstrate the potential of using these animals to investigate the role(s) of uterine mast cells and non-mast cell uterine histamine in the process of implantation and the formation of a decidual cell response.